4 Claims. (Cl. 229-45) wardly and inwardly into interengaging and/or interlocking relation with matching locking flaps on the ends of the wall panels of the body member and maintaining the iiaps in the closed interlocked position parallel to the body wall panels by attaching an encircling band thereabout. The interlocking ap closure system provides a seal under continuing tension between the flap folds at the ends of the body member panels and the underface of the cover member.

I'he present invention contemplates providing-a Drumpak or polygonal `container having closure means, as described, with an inner liner and with relatively rigid pads, conforming in shape to the horizontal cross-section of the body member of the Drumpak container, for closing the open ends of the liner. The liner is shorter than the body member panels by about twice the thickness of the board so that the upper faces of the closure pads, when in place, will be substantially in the plane of the end edges of the body panels and in atwise contact with the underface of the Drumpak closure member in the closed position thereof. A sheet of highly resilient cushioning material of the same general shape as the closure pads, but of larger dimeter, may be secured to ,the inner face of the pad. When the pad with the lcrushioning material is placed over the open end of the hner and the body aps are in their initial outwardly extending position, a portion of the cushioning material will Thus, when the closure member is secured to the body member, the resilient cushioning material will be interposed and compressed over several areas, namely, between the end edges of the liner and the side edges of the pad, between the side edges of the pad and the upper margin of the body panels, between the fold at the upper end of the body panel and the underface of the closure member and also between the interengaged or interlocked body and closure aps. The several compressed areas of the cushioning material serve to distribute the force of any sharp impact incident to handling and transportation over a much greater area of the container structure and thus protect the integrity of the closure structure and provide a permanent tension seal which is proof against sifting of materialsV not only in pellet and granular form, but of fractional micron particle size, such as impalable powder.

Highly resilient materials especially suitable for the purpose of the invention are wood cellulose fibers, pararent 2,794,588 Patented June 4, 1957 ice pose of the invention are laminated, creped cellulose liber Wadding or cushioning materials known in the trade as Kimpak and cellulose ber padding known as Tufexf However, any other highly resilient material of suitable thickness may be interposed between the elements of the Drumpak container for the purposes hereinbefore described.

An object of the invention is to provide an improved sift-proof seal for the ends of polygonal containers of the kind generally referred to as Drumpaks by interposing a sheet of highly resilient cushioning material between the closure panel and the upper end edge of the body member and between the interlocked closure and body aps yof the Drumpak.

Another object is to provide a polygonal container or Drumpak with an inner open ended liner and a closure pad of substantially the same shape as the horizontal cross-section of the body member, positioned over the free end edges of the liner and in contact with the underface of the closure member, and an interposed sheet of highly resilient cushioning material between the closure pad and the upper end edges of the liner and also between the upper end edges of the container body and the underface of the closure member and-extending between the interlocked closure aps, forming an effective barrier to the passage of nely divided material, even impalable powdery substances.

These and other `objects will be apparent to those skilled in the art upon a full and complete understanding of the construction and operation of the invention.

The invention also consists in the parts, arrangements and combinations of the parts hereinafter described.

The accompanying drawings form a part of this speciiication and like numerals and symbols therein appearing refer to like parts wherever they occur.

Fig. l is a plan view `of the top of a polygonal Drumpak container with portions of the closure member and the closure pad cut away to show a portion of the Wall structure and the cushioning material;

Fig. 2 is a front elevation of the Drumpak container with the closure members attached and secured in closed position by encircling bands;

Fig. 3 is a vertical, sectional View of the container of Fig. 2 taken in the direction of the arrows 3-3;

Fig. 4 is a vertical, sectional View of the container showing the cover member in an intermediate stage of closing;

Fig. 5 is a vertical cross-sectional view of the upper portion of the container of Fig. 2 taken in the direction of the arrows 5 5; y

Fig. 6 is an exploded perspective view of the several elements of the top and bottom closures of the container positioned in the order in which they are combined with the body section;

Fig. 7 is an enlarged plan view of a corner of the containershown in Fig. 2; and

Fig. 8 is an enlarged perspective view of a corner and the adjacent walls of the container adjacent the interlocking closure flaps.

A fully erected octagonal Drumpak container of a preferred form of interlocking closure means with the top and bottom closures attached is shown at A in Fig. 2. The container comprises an octagonal body section B,

tinuously as long as the encircling band -|Fig. 6, with top and bottom closure flaps 10, integral With body panels 11 and foldable about the scores 12. The cover member C consists of a cover panel 13 similar 1n -shape to a horizontal cross-section of the body/member VB. 4Each side edge 14 of the cover panelrhas an integral closure ange 15 withV notches 16 for receiving an encircling band 17, Fig. 2, in therclosed position of the cover member. Each of the ilanges 15 has a locking ap extension 18 which is rebent about score 179 which becomes interlocked with the body ap 1Q in the closed position of the cover member.` flhe body member B has Van interior, open-ended liner 20 snugly tting the interior thereof with its end edges 21 terminating a slight distance inside the ends of the body panelsp11. A closure pad 22 corresponding in shape to a horizontal cross-section ofthe interior of the body member B, with side edges 23 corresponding to the width of the body panels 11 is adapted to lit snugly inside the body member B over the ends 21 of the liner 20. A sheet of highly resilient cushioning material 24, which may be of the'same outline as the closure panel 13, and the closure disl; 22, which is .somewhat larger in diameter than either and hasn side edges 25, is adapted to Yextend over the body aps where they are extended outwards from the body member B. Y

The closure member C may be attached to the body member B by first folding the body aps 10 outwardly. The sheet of cushioning material 24 mayV be ,attached to the underside of the closure pad 22 in any convenient way, for example, by glue or other'suitable means with ,the edgesV 25 of the cushioning material in parallelalign- 'ment with the edges 23 of the closure pad. The cushioning material and closure pad are then placed over the outwardly folded body tlaps 10 with the side edges 23 of the closure pad in vertical alignment with the end edges 21 of the inner liner 2t)V of the body member l5.V The side edgesV 25 of the cushioning material will now extend over- 'a substantial portion'of the body aps 10. The cover member C is next placed` over the closure pad 22with the sides 14 of the cover panel in substantially vertical alignment with the side edges 23 of the closure pad and the outer face of the body panels 11. The anges of the cover member are then folded downwardly andthe closure aps 18 rebent about the score 19 and interposed between the body panel 11 and the body flaps 10. The downward movement of the flanges 15 is continued until they are in substantially parallel relation to the body panels 11 with the rebent ilaps 18 in flatwise relation to the panels 1 1 as Yshown most clearly in Fig. 5. A In this closed position, the cushioning sheet 274 will be compressed over the top edge 271 of the liner and in compressed, abutting relation to the inner face of the body panels 11. It will also be compressed between the sides 23 of the pad 22 and the uppermargin of the body panel Y11. Another compressed area of the sheet is between the underface of the cover panel 13 and the fold 26 of ,the body llaps over the end of the body panel and it will also be tightly held between the interlocked body flaps 10 and the closure ilanges 15 by the encircling band 17 which is held in place by the notches 16. r

As the closure flanges 15 are forced downward into parallelism with the body panels 11 and the rebent locking flaps 18 interposed between the body llaps 10 and the wall panels 11, an increasing tension between the several adjacent parts of the body member B and the cover mem- Iber C gradually compresses the interposed cushioning material to'a relatively highdegree over the several relatively wide areas, as illustrated in Fig. 5, and this compression of the cushioning material is maintainedcon- 17 is in place around the flanges 15. These compressed portions of the cushioning material form a very elective dam or'seal to the passage of very finely divided material, for example,

particles of fractional micron size, either from within the container outwardly or vice versa.

The highly re- 4 silient pad of cushioning material between the elements of the body member and the closure member serve a further important feature of distributing the force of the sharp impacts incident to handling and transportation and to minimize or substantially eliminate the possibility of such impacts impairing any portion of the tension seal provided by the invention.

The hereinbefore described method of interlocking the cover and the body flaps of the Drumpak container is a preferred system but similar results may be obtained by folding cooperating pairs of aps into parallelism ywith the body panels in modified relation to each other. For example, by adjusting the lengths of the covei aps`18 and the body aps 10 so that their free ends will be in abutting relation under tension in the closed position of the Drumpak container cover. Variations of suitable ap interengaging methods are described in the United States patents hereinbefore mentioned. Y Y' The particular embodiment described and the variations thereof are intended to be illustrative and notrestrictive, and it is to be understood that the invention herein is applicable to further modied forms of Drumpak containers and all such modifications which are similar or equivalent thereto come equally within the claims next appearing.

What we claim is :Y Y l 1. A sift-proof closure'means for a polygonal container comprising a body member formed of a plurality of connected` together wall panels each having outer marginal flaps, an inner liner slightly less in'length than the body wall panels, a closure pad corresponding in shape to a horizontal cross section of the interior of the body member adapted to snugly t inside the end margins of the body member and seat on the free `end edges of the inner liner, and a cover panelY corresponding in shape to a cross section of said body member secured to the end of said body member by integral flanges on each side edge of said cover panel with locking flaps on their outer edges interengaged or interlocltedA with matching flaps 10u the ends of the body panels; said sift-proof closure means comprising a sheet of resilient cushioning material of greater diameter than said closure pad positioned on the underface of said closure pad and interposed and cornpressed between the upper free edges of said inner liner and the under face of the Vside margins of said closure pad, between the upper margin of said body panels and the side edges of the said closure pad and betweenithe fold of the closure flap at the upper edge of said body panel and the underface of said cover member.

2. The combinationl set forth and claimed Vin claim l wherein said cushioning material extends beyond the sides A of the cover panel into interposed relation between the Vinterlocked cover anges and body flaps.

Vflanges and body flaps;

4. A closure means for a polygonal container imper- Vmeable to solids of fractional micron size, said container comprising a plurality of connected together wall panels .forming an open ended body member, each of said panels having an integral end margin locking flap, an inner liner slightly less in length than the body wall panels for said lbody member with a rigid closure pad conforming in Y shape ltothe inner periphery of said body member positioned. over said liner with its side edges adjacent the end margins of the body panels and in vertical alignment Ywith the ends of said liner, and a cover member with side 'edges corresponding in .number to the body member panels, said cover member being secured to the end of eachV body member by integral marginal flanges on each side edge thereof with locking llaps on their outer edges interengaged or interlocked with said body member flaps, saidV impermeable closure comprising a pad ofhighly resilient cushioning material of greater diameter than said liner closure pad, said cushioning pad being secured to the underface of said closure pad and compressed between the interengaged body flaps and the cover member anges, between the upper end of the body walls and the underface of the closure member, between the upper end edges of said liner and the underface of said liner c1osure pad and also between the outer edges of said liner closure pad and the end margin of said body panel.